Implantable devices using rechargeable zero-volt technology lithium-ion batteries

Abstract

An implantable medical device, such as an implantable pulse generator (IPG) used with a spinal cord stimulation (SCS) system, includes a rechargeable lithium-ion battery having an anode electrode with a substrate made substantially from titanium. Such battery construction allows the rechargeable battery to be discharged down to zero volts without damage to the battery. The implantable medical device includes battery charging and protection circuitry that controls the charging of the battery so as to assure its reliable and safe operation. A multi-rate charge algorithm is employed that minimizes charging time while ensuring the battery cell is safely charged. Slow charging occurs at lower battery voltages (e.g., battery voltage below about 2.5 V), and fast charging occurs when the battery voltage has reached a safe level (e.g., above about 2.5 V). When potentially less-than-safe very low voltages are encountered (e.g., less than 2.5 V), then very slow (trickle) charging occurs to bring the battery voltage back up to the safer voltage levels where more rapid charging can safely occur. The battery charging and protection circuitry also continuously monitors the battery voltage and current. If the battery operates outside of a predetermined range of voltage or current, the battery protection circuitry disconnects the battery from the particular fault, i.e. charging circuitry or load circuits.

1. An implantable device comprising:
 electronic circuitry that performs a specified function; 
 an implantable rechargeable battery that provides operating power for the electronic circuitry; and 
 battery charging and protection circuitry for receiving power from an external charger and controls the charging of the rechargeable battery to protect the rechargeable battery from overcharge and undercharge conditions; 
 wherein the implantable rechargeable battery comprises a lithium-ion or lithium-ion polymer battery having an anode electrode with a substrate made substantially from a metal selected from the group consisting of titanium, titanium alloys, nickel, nickel alloys, and stainless steel, wherein the rechargeable battery may discharge to zero volts without damage, 
 wherein the battery charging and protection circuitry applies a trickle charge current I 1  to the rechargeable battery when a rechargeable battery voltage ranges from zero volts to a first voltage V 1 , and applies a second charging current I 2  to the rechargeable battery when the rechargeable battery voltage ranges from the first voltage V 1  to a second voltage V 2 , and 
 wherein the trickle charge current I 1  is less than the second charging current I 2 . 
 
     
     
       2. The implantable device of  claim 1  wherein the first voltage V 1  comprises about 2.5 V, and the second voltage V 2  comprises about 4.1 V.